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| Titel |
Underlying mechanisms of transient luminous events: a review |
| VerfasserIn |
V. V. Surkov, M. Hayakawa |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 30, no. 8 ; Nr. 30, no. 8 (2012-08-17), S.1185-1212 |
| Datensatznummer |
250017254
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1185-2012.pdf |
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| Zusammenfassung |
| Transient luminous events (TLEs) occasionally observed above a strong
thunderstorm system have been the subject of a great deal of research during
recent years. The main goal of this review is to introduce readers to
recent theories of electrodynamics processes associated with TLEs. We
examine the simplest versions of these theories in order to make their
physics as transparent as possible. The study is begun with the conventional
mechanism for air breakdown at stratospheric and mesospheric altitudes. An
electron impact ionization and dissociative attachment to neutrals are
discussed. A streamer size and mobility of electrons as a function of
altitude in the atmosphere are estimated on the basis of similarity law. An
alternative mechanism of air breakdown, runaway electron mechanism,
is discussed. In this section we focus on a runaway breakdown field,
characteristic length to increase avalanche of runaway electrons and on the
role played by fast seed electrons in generation of the runaway breakdown.
An effect of thunderclouds charge distribution on initiation of blue jets
and gigantic jets is examined. A model in which the blue jet is treated as
upward-propagating positive leader with a streamer zone/corona on the top is
discussed. Sprite models based on streamer-like mechanism of air breakdown
in the presence of atmospheric conductivity are reviewed. To analyze
conditions for sprite generation, thunderstorm electric field arising just
after positive cloud-to-ground stroke is compared with the thresholds for
propagation of positively/negatively charged streamers and with runway
breakdown. Our own estimate of tendril's length at the bottom of sprite is
obtained to demonstrate that the runaway breakdown can trigger the streamer
formation. In conclusion we discuss physical mechanisms of VLF (very low
frequency) and ELF (extremely low frequency) phenomena associated with
sprites. |
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